1. Technical Field
This invention relates to pipe assemblies and, in particular, to an intumescent fire stopping pipe collar having interlocking tabs.
2. Description of the Related Art
Practical installations of pipe, such as PVC pipe, in residential and commercial construction require that the pipe pass through or penetrate floors and walls. At the junction between the floor or wall and the pipe, there must be a hole large enough for the pipe to pass through and to allow positioning of the pipe. In practice, the hole may fit the pipe tightly or may be somewhat larger than the outside diameter of the pipe. A problem arises when the surface being penetrated is also fire resistant. In order to maintain the fire integrity of the penetration system, the pipe and annular space surrounding the pipe must be protected at a level equal to the protection offered by the original floor or wall. Fire protection schemes must include provisions for the melting of plastic pipe and insulation as well as maintaining the structural integrity of the penetrated surface.
A variety of methods have been employed to achieve the proper level of fire protection. One of the most popular methods is the use of intumescent, or expanding, materials. Upon application of heat, these materials expand several times their original volume to fill spaces or voids left by melted plastic pipe. For smaller sizes of pipe, filling the annular space with intumescent caulk is adequate. However, this method is limited by variations in hole diameter. Some hole diameters are either too large or too small to be practically filled with caulk. Also, for larger pipe sizes, more intumescent material must be used in a caulk system than is typically practical.
One method to control both the amount intumescent material used and the mechanical integrity of the pipe/fire-stop material is to surround the pipe with a metal shroud or fire-stop collar and to place the intumescent fill material between the collar and the plastic pipe. The collar is anchored to the penetrated surface. In part, the total system integrity is determined by the soundness of the connection between the collar and the penetrated surface. In many cases, multiple anchor points between the collar and the surface must be used.
Both light weight and heavy metal collars have been produced. Collars made from heavy gauge metal must be preformed at the factory to aid in the installation process. On the other hand, collars made from light gauge metal may be partially or entirely formed in the field. The tradeoff between field- or factory-formed collars becomes one of economics; however, factory-formed parts are generally more economical than field-formed parts for all but the most custom conditions. Since the metal collar must be placed around the pipe, the heavy gauge collar is generally made in two or more parts. The parts are held together with hinges, locking bars, hose clamps, clasps, fasteners, or a variety of tongue and groove arrangements.
One important feature of the fire stop collar is a tab that accepts a fastener to facilitate the attachment of the collar to the penetrated surface. The anchor tab can be integral, detachable, field, or factory formed. Anchor tabs may be symmetrically or asymmetrically disposed around the pipe. The number of anchor tabs is generally dictated by the structural integrity requirements of the fire protection system. While more tabs will increase the structural soundness, fewer tabs will reduce installation labor. Also, to reduce the number of tabs, stiffening flanges extending perpendicular to the surface of the tab may be added.
On the application of heat, for example in a fire, the intumescent material swells to fill the annular space and voids left by melted plastic pipe. To maximize the radially inward force of the intumescent material to close off any voids or spaces, a flange may be formed on the outstanding edge of the body of the collar. This flange prevents intumescent material from extruding longitudinally along the axis of the pipe. Also, the flange may be notched to facilitate forming the collar into a cylinder surrounding the pipe. The flange also adds stiffness to the outstanding edge of the collar body.
Existing fire stop collars utilize hinge-and-clasp mechanisms, lock bars, or hose clamps to hold the collar in a position surrounding the pipe. Those features must be manufactured separately from the collar, adding to the manufacturing cost. In addition, those types of clamping mechanisms are relatively difficult to use in the field. The hole in the floor or wall through which the pipe must pass is in many cases nearly the same size as the circumference of the pipe, leaving little room for the installer to manipulate the clamping mechanism. In addition, the installer must use one hand to hold the collar in place around the pipe, leaving only the other hand to operate the clamps, screws or lock bars.